The present invention relates to a method for the preparation of cyclohexanone or, more particularly, to a method for the preparation of cyclohexanone by the oxidation of cyclohexene in the liquid phase with molecular oxygen in the presence of a catalyst.
Cyclohexanone is a very useful organic compound in chemical industry, for example, as the starting material of the monomers of nylons and polyesters and as the intermediate for the synthesis of various kinds of useful derivatives by virtue of the high reactivity thereof.
Along with the traditional processes for the preparation of cyclohexanone by the catalytic reduction of phenol and the catalytic dehydrogenation or oxidation of cyclohexanol, the currently practiced process therefor is the air-oxidation of cyclohexane in the liquid phase. This process is, however, very unsatisfactory from the standpoint of the efficiency of the process.
For example, the cyclohexanone product formed in the liquid phase is more susceptible to the oxidation under the manufacturing conditions of the autoxidation than the cyclohexane as the starting reactant so that the conversion of the cyclohexane cannot be sufficiently high rarely to exceed 7 to 8% since otherwise the cyclohexanone once formed in the liquid phase is lost by the further oxidation.
In addition, the selectivity of the reaction, i.e. the proportion of the consumed starting reactant converted to the desired product, is also unsatisfactory and usually in the range of 70 to 80% even when calculated as the total value for cyclohexanone and cyclohexanol, which latter can be converted to the desired cyclohexanone by undertaking the catalytic dehydrogenation.
Various attempts have been made to enhance the effeciency of the above process, in particular, as directed to the improvement of the catalyst used in the reaction but with no noticeable success due to the high reactivity of cyclohexanone.
Accordingly, it has been eagerly desired to develop a novel and efficient method for the industrial preparation of cyclohexanone.